Abstarct: Sub-fractional horse power rating hysteresis motor as an exciter less synchronous machine has found wide applications. Hysteresis motors becoming dominant machines with cost the competitiveness of semi hard permanent magnet materials in the some particular applications. This motor has some favorite features such as constant torque during run up, low startup current and noiseless operation. Simple and robust rotor’s structure, low starting current (around 1.2 to 1.5 times of nominal current), constant torque, smooth and noiseless operation are the outstanding characteristics of hysteresis motor, which candidate these motors for high speed applications. However, low efficiency and low power factor are commonly mentioned as the main deficiencies of the hysteresis motors which can be improved somewhat with rotor substance and design contemplations. In this thesis two new structures named CDDHM (coreless dual rotor disc type hysteresis motor) and SDDHM (slotless dual rotor disc type hysteresis motor) for hysteresis motor are introduced and their operations are analyzed with some details. Electromagnetic field analysis of CDDHM and SDDHM are performed and steady state equivalent circuits baxsed on design parameters for both motors are deduced. A computer simulation algorithm is presented to predict the steady state operation characteristics of the motors. Electromagnetic characteristics of a steel alloy which contains iron, chrome, nickel, molybdenum and carbon (Fe-Cr-Ni-Mo-C) are presented and a new application for this steel as an alternative material for the rotor of hysteresis motor is investigated. Magnetic properties of Fe-Cr-Ni-Mo-C are compared with those of a few common magnetic materials which are used in the conventional hysteresis motors. The genetic algorithm is used to optimize the design of CDDHM and SDDHM motors. Optimized motors with different alloys use in the rotor are finally compared.